Nitrofurantoin
Information last updated October 2024
Most pregnancies result in healthy babies, but there are chances of complications and unexpected outcomes. These chances are called baseline risks. In Canada, the baseline risk of major birth defects is 3-5%. This means that 3-5 out of 100 babies born in the general population will be born with a major birth defect. There are also baseline risks for miscarriages (15-25 out of 100 pregnancies), premature birth and other outcomes. The information provided will summarize if taking this drug is likely to change these risks.
Summary: Studies looked at the rates of birth defects in over 13,000 pregnancies where nitrofurantoin was used in the first trimester. Most studies found that taking nitrofurantoin during pregnancy does not increase the risk of major birth defects above the baseline risk. An increased risk of orofacial clefts (an opening in the lip and/or roof of the mouth) was found in one database but not found in other studies. Even if the suggested risk of orofacial clefts exists, the chance of it occurring would be low. The lips and roof of mouth (palate) are formed by the 12th week of pregnancy. Once the lips and palate are formed, cleft lip and/or palate cannot occur. The available information does not show increased risks of other adverse pregnancy outcomes. To see more details, please click on the tabs below.
It is important to treat urinary tract infections in pregnancy, as untreated infections can lead to complications which may affect the pregnancy and the developing baby.
Nitrofurantoin should be avoided in pregnancy by those with glucose-6-phosphate dehydrogenase deficiency (G6PD).
Please consult with your health care provider if you are considering stopping or making any changes to your regular medications.
This information about nitrofurantoin is of a general nature and about medical use and does not replace the medical care and advice of your healthcare provider. For questions on dose, timing, side effects, interactions, etc. please consult your healthcare provider. Additionally, please read the patient insert provided with your medication.
Although participants in the studies referenced below may have used nitrofurantoin in various combinations, the studies usually do not provide detailed information on drug combinations. This makes it challenging to comment on the safety of using this medication in combination with others during pregnancy or lactation.
Nitrofurantoin is an antibiotic. It is used to treat urinary tract infections.
Nitrofurantoin is linked to a risk of hemolysis (break down of red blood cells) in those with G6PD. However, in most cases it is mild and does not cause serious health problems.
If the product you are using contains other active ingredients, please check our Exposures A to Z for available information on the ingredient(s).
Pronunciation
Please check back. We are in the process of reviewing if there is available information on the pre-pregnancy effects of nitrofurantoin.
Studies looked at the rates of birth defects in over 13,000 pregnancies where nitrofurantoin was used in the first trimester. Most studies found that taking nitrofurantoin during pregnancy does not increase the risk of major birth defects overall or for specific birth defects above the baseline risk. An increased risk of orofacial clefts (an opening in the lip and/or roof of the mouth) was found in one database but not in other studies. The baseline rate of orofacial clefts in Canada in 2023 was 1.5/1000 (https://health-infobase.canada.ca/congenital-anomalies/data-tool/). Even if the suggested risk of orofacial clefts exists, the chance of it occurring would be low (less than 3 in 1000). The lips and roof of mouth (palate) are formed by the 12th week of pregnancy. Once the lips and palate are formed, cleft lip and/or palate cannot occur.
Studies do not report higher rates of miscarriage, stillbirth (loss of a baby before or during delivery), premature birth (delivery before 37 weeks of pregnancy), or low birth weight when nitrofurantoin was used in pregnancy.
Please check back. We are in the process of reviewing if there is available information on the effects of paternal exposure to nitrofurantoin.
No increased risk of harmful effects to the newborn were found in a study that included over 5000 pregnancies exposed to nitrofurantoin.
There are case reports of hemolytic anemia (red blood cells being broken down) in newborns who were exposed to nitrofurantoin in late pregnancy. A study including over 900 newborn infants who were exposed to nitrofurantoin in the last 30 days of pregnancy did not find an increased risk of hemolytic anemia. The American College of Obstetricians and Gynecologists (ACOG) suggests that nitrofurantoin can be used as first-line treatment of urinary tract infections in the 2nd and 3rd trimesters.
If you are taking medications and you notice any new health concerns or symptoms in your nursing infant, please contact their health care provider. In case of emergency, please go to the emergency room or call 911.
If you are taking a medication or substance while providing your breastmilk to an infant, you need to know how much of the medication or substance is passing into your milk. One of the commonly used measurements to estimate this is the Relative Infant Dose (RID). The RID is estimated by comparing the dose of drug taken in by the infant through breastmilk to the dose that the nursing parent takes. Most medications with an RID of less than 10% are usually compatible with nursing a healthy infant. The RID does not need to be calculated for each person because most of the time it is expected to be similar to what has been found in research studies. We will provide the RID in the information below, when available.
Nitrofurantoin passes into breastmilk in variable amounts. It was not detected in breastmilk of at least 9 women taking 400 mg nitrofurantoin daily but was detected in the breastmilk of 10 other women taking 150-400 mg nitrofurantoin daily. Based on the detected breastmilk levels, the RID of nitrofurantoin is estimated to be 1.1% to 6.0%.
In one case series, diarrhea was reported in two out of six infants exposed to nitrofurantoin through breastmilk. Please reach out to a healthcare provider if you notice any changes in your baby (such as diarrhea or thrush).
Individuals providing their breastmilk to infants with G6PD deficiency or who are less than 9 days old, should not nurse if treated with nitrofurantoin. If providing breastmilk to an infant less than one month old, an alternative antibiotic is preferred. If an alternative is not available, the use of nitrofurantoin would not be a reason to avoid nursing if the infant is 9 days or older.
There are studies looking at nitrofurantoin use in pregnancy and child’s health later in life. However, these studies have issues that prevent us from drawing conclusions.
Costs of some medications are covered for eligible people under provincial or national Indigenous drug benefit plans. Please visit the Ontario Drug Benefit (ODB) program Check medication coverage or the Non-Insured Health Benefits (NIHB) program Drug Benefit List to check if nitrofurantoin is covered for you.
Medications, if not taken as prescribed, if taken beyond the prescribed amount, or if taken in combination with certain other drugs, may cause harm to you and/or your pregnancy or your nursing child.
If you are using drugs or medications for non-medical reasons or beyond what was recommended by a healthcare practitioner and you are pregnant, providing your breastmilk to an infant, or parenting please click Harm Reduction for additional information. In case of emergency, please go to the emergency room or call 911.
Pregnancy:
Studies examining rates of birth defects included over 13,000 pregnancies where nitrofurantoin was used in the first trimester. Most studies found that use of nitrofurantoin during pregnancy does not increase the risk of major birth defects overall or for specific birth defects above the baseline risk. An increased risk of orofacial clefts was reported in one database (National Birth Defects Prevention Study) but not found in other studies. The rate of orofacial clefts in Canada in 2023 was 1.5/1000 (https://health-infobase.canada.ca/congenital-anomalies/data-tool/). Even if the suggested increased risk of orofacial clefts was accurate, the absolute risk is low (less than 3 in 1000). The lips and palate are formed by the 12th week of pregnancy. Once the lips and palate are formed, cleft lip and/or palate cannot occur.
No increased risk of miscarriage, stillbirth, premature birth, or low birth weight were reported with nitrofurantoin use in pregnancy.
No increased risk of adverse effects in newborns (low Apgar score at 5 minutes and transfer to NICU) exposed to nitrofurantoin in utero was reported in a study that included over 5000 pregnancies.
There are case reports of hemolytic anemia in neonates who were exposed to nitrofurantoin in late pregnancy. A study including over 900 neonates who were exposed to nitrofurantoin in the last 30 days of pregnancy did not find an increased risk of hemolytic anemia. The American College of Obstetricians and Gynecologists (ACOG) indicates that nitrofurantoin can be used as first-line treatment of urinary tract infections in the 2nd and 3rd trimesters.
There are studies looking at nitrofurantoin use in pregnancy and child’s health later in life. However, the studies have methodological limitations. More research is needed to draw conclusions.
Lactation:
One of the factors that helps to determine if a medication is compatible with nursing is the Relative Infant Dose (RID). The RID provides an estimate of infant’s exposure to a medication through breastmilk. It is the ratio between the infant’s and the nursing individual’s weight-adjusted doses. The infant weight adjusted dose is estimated based on the concentration of medication in breastmilk, and an assumption of infant daily milk consumption of 150 ml/kg/day. In general, for infants with normal growth and development, most medications with an RID of less than 10% are considered compatible with nursing. The RID does not account for infant’s drug metabolism, clearance, or infant blood levels. Although some variability may exist in the RID, in most cases the estimated RID is adequate for clinical purposes and does not need to be calculated for each individual. We will provide the RID in the information below, when available.
Nitrofurantoin was not detected in breastmilk of at least 9 women taking 400 mg nitrofurantoin daily. Based on breastmilk levels of an additional 10 women who received 150-400 mg of nitrofurantoin daily, the RID is estimated to be 1.1% to 6.0%.
Information on effects on the nursing infants is limited to one study that reported diarrhea in two out of six infants exposed to nitrofurantoin through breastmilk. Advising the parent(s) to look out for diarrhea and thrush in the infant may be considered.
Individuals providing their breastmilk to infants with G6PD deficiency or who are less than 9 days old, should not nurse if treated with nitrofurantoin. If providing breastmilk to an infant who is 9 days to one month old, an alternative antibiotic is preferred. If an alternative is not available, the use of nitrofurantoin would not be a reason to avoid nursing.
Harm Reduction:
If your patient may be using drugs or medications not as indicated during pregnancy, while providing breastmilk to an infant, or parenting please click Harm Reduction for additional information. In case of emergency, please advise them to go to the emergency room or call 911.
For additional resources see Health Canada Drug and Natural Health Product Monographs, Making Sense of Risk and Statistics.
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Disclaimer
First Exposure does not offer health care treatment. If you have an urgent question about your pregnancy or your baby’s health, you should contact your health care provider directly. If you don’t have a health care provider and you live in Ontario, you have a variety of health care options. In the case of an emergency, visit a hospital emergency room or call 911.